Deck Pic Posted November 8, 2012 Share Posted November 8, 2012 It was 14.5" for quite a while...how can it suddenly change? Link to comment Share on other sites More sharing options...
Ian Posted November 8, 2012 Share Posted November 8, 2012 looks like they changed Feb from 4.8 to 5.7 lol Link to comment Share on other sites More sharing options...
mattie g Posted November 8, 2012 Share Posted November 8, 2012 It sucks either way. Link to comment Share on other sites More sharing options...
Bob Chill Posted November 8, 2012 Share Posted November 8, 2012 Wonder what it is without 2010? Link to comment Share on other sites More sharing options...
Ian Posted November 9, 2012 Share Posted November 9, 2012 Wonder what it is without 2010? We went over this to some degree when the new norms came out, when it seemed like they basically threw out 2010. They are not completely transparent with their methodology so it's anyone's guess but I wonder if the change has to do with 2010. Link to comment Share on other sites More sharing options...
Bob Chill Posted November 9, 2012 Share Posted November 9, 2012 Maybe they just corrected all the obvious measurement errors at DCA. Seemed like every storm didn't seem right. Not one time can I remember in the last 6+ years anybody saying that the DCA measurement seemed high. Link to comment Share on other sites More sharing options...
Ian Posted November 9, 2012 Share Posted November 9, 2012 Maybe they just corrected all the obvious measurement errors at DCA. Seemed like every storm didn't seem right. Not one time can I remember in the last 6+ years anybody saying that the DCA measurement seemed high. I don't think any of the monthly data changed though I only glanced. I'm assuming it was either an error or they redid something in their smoothing method. Of course, this makes the article I wrote about Feb being less snowy than Jan wrong. Link to comment Share on other sites More sharing options...
usedtobe Posted November 9, 2012 Share Posted November 9, 2012 The calculations should be pretty easy so I'm surprised by the change. Maybe somewhere on the spread sheet, a Feb snow year was typed it or entered wrong? Whatever, I've got a slide to correct. Link to comment Share on other sites More sharing options...
Ian Posted November 9, 2012 Share Posted November 9, 2012 The calculations should be pretty easy so I'm surprised by the change. Maybe somewhere on the spread sheet, a Feb snow year was typed it or entered wrong? Whatever, I've got a slide to correct. I don't get why it's not a straight average. Rain is. Not that an avg would be representative per se but the smoothing barely changes the numbers and it's not transparent how they get to the calculation. Link to comment Share on other sites More sharing options...
Bob Chill Posted November 9, 2012 Share Posted November 9, 2012 I really have no idea why and can't find any public record of the methodology. I've also never looked for the "math". I've always assumed the calcs were sound. If anybody finds something please post it. Link to comment Share on other sites More sharing options...
Ian Posted November 9, 2012 Share Posted November 9, 2012 I really have no idea why and can't find any public record of the methodology. I've also never looked for the "math". I've always assumed the calcs were sound. If anybody finds something please post it. I guess it's possible something's just up with LWX's numbers. But this is what you get in comparison: Monthly 30-yr Avg ending 10-11 via LWX Nov - 0.5 Dec - 2.3 Jan - 5.7 Feb - 5.8 Mar - 1.3 Tot - 15.6 NCDC/LWX norms Nov - 0.5 Dec - 2.3 Jan - 5.6 Feb - 5.7 Mar - 1.3 Tot - 15.4 The raw page is here: http://www1.ncdc.noa...743.normals.txt Deciphering: http://www1.ncdc.noa...2010/readme.txt The months all have a C by them which indicates the full record is used. I believe Feb used to have an S but it's been a while since I looked maybe I made that up... tho it would explain the lower number initially. Still, Jan and Feb don't match using a straight avg. An avg by season comes out to 15.62 unrounded as well. Haven't looked at the other stations, perhaps I should. I know LWX has mis-entered some data in the past so maybe their months are off somewhere. Link to comment Share on other sites More sharing options...
usedtobe Posted November 9, 2012 Share Posted November 9, 2012 I guess it's possible something's just up with LWX's numbers. But this is what you get in comparison: Monthly 30-yr Avg ending 10-11 via LWX Nov - 0.5 Dec - 2.3 Jan - 5.7 Feb - 5.8 Mar - 1.3 Tot - 15.6 NCDC/LWX norms Nov - 0.5 Dec - 2.3 Jan - 5.6 Feb - 5.7 Mar - 1.3 Tot - 15.4 The raw page is here: http://www1.ncdc.noa...743.normals.txt Deciphering: http://www1.ncdc.noa...2010/readme.txt The months all have a C by them which indicates the full record is used. I believe Feb used to have an S but it's been a while since I looked maybe I made that up... tho it would explain the lower number initially. Still, Jan and Feb don't match using a straight avg. An avg by season comes out to 15.62 unrounded as well. Haven't looked at the other stations, perhaps I should. I know LWX has mis-entered some data in the past so maybe their months are off somewhere. Thanks for doing the numbers. I guess I'll use the NCDC numbers for an average if I discuss it in an article. Link to comment Share on other sites More sharing options...
MN Transplant Posted November 9, 2012 Share Posted November 9, 2012 I'm getting 463" from LWX's page, and 463.4" from the NCDC text for the period. Looks like the extra 0.4" comes from the conversion back and forth to mm, so I actually like LWX's number better. Both divide to 15.4". Ian - isn't the average going to end with the season of 09-10? Link to comment Share on other sites More sharing options...
Ian Posted November 9, 2012 Share Posted November 9, 2012 I'm getting 463" from LWX's page, and 463.4" from the NCDC text for the period. Looks like the extra 0.4" comes from the conversion back and forth to mm, so I actually like LWX's number better. Both divide to 15.4". Ian - isn't the average going to end with the season of 09-10? Yes. Forget my calc. It is just an avg. Link to comment Share on other sites More sharing options...
ORH_wxman Posted November 9, 2012 Share Posted November 9, 2012 The average is technically annual though, isn't it? So the last numbers would be the 2010-2011 season before New Years 2011. Though this should not change the numbers much at all...if any. Link to comment Share on other sites More sharing options...
RodneyS Posted November 9, 2012 Share Posted November 9, 2012 So the last numbers would be the 2010-2011 season before New Years 2011. Though this should not change the numbers much at all...if any. No, the most recent 30-year normal -- which is identical to the 30-year average -- used by the National Weather Service is calculated by beginning with the 1980-1981 snow season and ending with the 2009-2010 snow season. The following link shows the 1981-2010 monthly normals (averages) for DCA at the bottom of the page -- http://www.erh.noaa....dca/dcasnow.txt Link to comment Share on other sites More sharing options...
ORH_wxman Posted November 9, 2012 Share Posted November 9, 2012 No, the most recent 30-year normal -- which is identical to the 30-year average -- used by the National Weather Service is calculated by beginning with the 1980-1981 snow season and ending with the 2009-2010 snow season. The following link shows the 1981-2010 monthly normals (averages) for DCA at the bottom of the page -- http://www.erh.noaa....dca/dcasnow.txt I'm pretty sure NCDC uses annual averages which would be different than the NWS page you linked. I personally prefer the seasonal one for snowfall. Link to comment Share on other sites More sharing options...
RodneyS Posted November 9, 2012 Share Posted November 9, 2012 I'm pretty sure NCDC uses annual averages which would be different than the NWS page you linked. I personally prefer the seasonal one for snowfall. If you use the 1981-2010 calendar years to compute the 30-year normal (average) for snowfall at DCA, it is 0.1 inch higher, at 15.5 inches per year. By the way, historical DC January and February snowfall (beginning with the 1884-1885 snow season and ending with the 2011-2012 snow season) has averaged just what it has over the recent 1981-2010 normal period -- 5.6 inches for January and 5.7 inches for February. However, there has been a big drop-off in December and March snow. The former has averaged 3.0 inches historically versus only 2.3 inches during 1981-2010, and the latter has averaged 2.9 inches historically versus only 1.3 inches during 1981-2010. Link to comment Share on other sites More sharing options...
clskinsfan Posted November 10, 2012 Share Posted November 10, 2012 If you use the 1981-2010 calendar years to compute the 30-year normal (average) for snowfall at DCA, it is 0.1 inch higher, at 15.5 inches per year. By the way, historical DC January and February snowfall (beginning with the 1884-1885 snow season and ending with the 2011-2012 snow season) has averaged just what it has over the recent 1981-2010 normal period -- 5.6 inches for January and 5.7 inches for February. However, there has been a big drop-off in December and March snow. The former has averaged 3.0 inches historically versus only 2.3 inches during 1981-2010, and the latter has averaged 2.9 inches historically versus only 1.3 inches during 1981-2010. Thats an interesting fact that early and late in the season we are losing snow. It would make sense in a climate change type of scenario. But obviously the sample size is small. Link to comment Share on other sites More sharing options...
RodneyS Posted November 10, 2012 Share Posted November 10, 2012 Thats an interesting fact that early and late in the season we are losing snow. It would make sense in a climate change type of scenario. But obviously the sample size is small. True, but if you look at recent March temperatures it's pretty obvious that it has simply been too warm to obtain much snow in DC. During 1871-1900, March averaged 41.6 degrees in DC, whereas during 1981-2010, March averaged 46.9 degrees in DC. To put that latter figure in perspective, during 1871-1900 November averaged 45.0 degrees in DC. So March is now warmer in DC than November used to be. December has not warmed as much as March has in DC, but it is still 3.3 degrees warmer (36.5 degrees average during 1871-1900 versus 39.8 degrees average during 1981-2010). So, it makes sense that there has been a decline in December snow here, but that the decline has been much more modest than in March. Link to comment Share on other sites More sharing options...
mattie g Posted November 10, 2012 Share Posted November 10, 2012 True, but if you look at recent March temperatures it's pretty obvious that it has simply been too warm to obtain much snow in DC. During 1871-1900, March averaged 41.6 degrees in DC, whereas during 1981-2010, March averaged 46.9 degrees in DC. To put that latter figure in perspective, during 1871-1900 November averaged 45.0 degrees in DC. So March is now warmer in DC than November used to be. December has not warmed as much as March has in DC, but it is still 3.3 degrees warmer (36.5 degrees average during 1871-1900 versus 39.8 degrees average during 1981-2010). So, it makes sense that there has been a decline in December snow here, but that the decline has been much more modest than in March. I think you have to take into account where those obs were taken. Big difference between the old location and the current one. That's not to dismiss the matter altogether, but I'd imagine the current location skews the numbers upwards by quite a bit. Link to comment Share on other sites More sharing options...
RodneyS Posted November 10, 2012 Share Posted November 10, 2012 I think you have to take into account where those obs were taken. Big difference between the old location and the current one. That's not to dismiss the matter altogether, but I'd imagine the current location skews the numbers upwards by quite a bit. I agree that's an issue, but for whatever reason something dramatic took place with respect to March temperatures in DC between the first 30-year measuring period (1871-1900) and the second (1901-1930). With the measuring location the same (Weather Bureau Office at 24th and M Streets, NW Washington), the average March warm-up between those periods was 3.4 degrees, versus a yearly average warm-up of only 0.4 degrees. Since the 1901-1930 measuring period, with the measuring location shifting to DCA, the average March warm-up (through 1981-2010) has been only 1.9 degrees, versus a yearly average warm-up of 2.9 degrees. However, with 1901-1930 March temperatures already averaging 45.0 degrees in DC, any increase above that has been very detrimental to snow. Perhaps a resident weather historian can explain why there was such a dramatic warm-up in March temperatures here from the first to the second measuring periods. Link to comment Share on other sites More sharing options...
mattie g Posted November 10, 2012 Share Posted November 10, 2012 Interesting. Thanks for the info, Rodney. Out of sheer intellectual curiosity, do you have info on (or can you show me where to find) say...the top ten DJF record highs and the top ten DJF record lows? I'm curious about about the range of record highs and lows during winter. (Sorry for the threadjack) Link to comment Share on other sites More sharing options...
RodneyS Posted November 10, 2012 Share Posted November 10, 2012 Interesting. Thanks for the info, Rodney. Out of sheer intellectual curiosity, do you have info on (or can you show me where to find) say...the top ten DJF record highs and the top ten DJF record lows? I'm curious about about the range of record highs and lows during winter. (Sorry for the threadjack) Monthly and seasonal DC temperatures are available here -- http://www.erh.noaa....ca/dcatemps.txt The top ten (tie for 10th) warmest DJF (meteorological) DC winters are (average Fahrenheit temperatures, with February given equal weight to December and January): 1931-32: 44.6 1889-90: 44.3 2011-12: 43.4 2001-02: 43.2 1949-50: 42.9 1997-98: 42.5 1948-49: 42.2 1990-91: 42.0 1996-97: 41.6 1974-75: 41.5 1879-80: 41.5 The top ten coldest DC meteorological winters are: 1904-05: 29.0 1903-04: 29.4 1917-18: 29.5 1880-81: 29.8 1935-36: 30.8 1892-93: 31.0 1919-20: 31.3 1894-95: 31.7 1884-85: 31.9 1962-63: 31.9 Link to comment Share on other sites More sharing options...
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